New clip-on mosquito repellent has drawbacks

Off! Clip-on uses a fan to surround the user with protection without having to spray it on the skin, but the device doesn't work well in heavy concentrations of pests.

Sometimes it's hard to tell what's more annoying -- mosquitoes or mosquito repellent. If you spray yourself down with a typical repellent before a picnic, you can expect your potato chips and fried chicken to have a distinct DEET aftertaste. And the car ride home? Better roll down the windows if you value fresh air.

But there's another option. As you may have seen on TV ads, SC Johnson has come out with Off! Clip-on, a product that promises to repel mosquitoes without any spray or odor. The plastic device, about the size of a hockey puck, contains a battery-powered fan that quietly surrounds the user with the repellent, a chemical called metofluthrin.

You can buy Off! Clip-on at drugstores and department stores, if you're lucky enough to find some in stock. Sales are so brisk that many stores are sold out. "People love the idea of not having to spray themselves with anything," says Chester Moore, professor of medical entomology at Colorado State University in Fort Collins.

The device costs a little less than $10, batteries included. According to the package, it contains enough repellent to last 12 hours. Repellent refills cost about $5 each.

The claims

According to the package label, Off! Clip-on offers "head to toe protection" from mosquitoes. The product website claims that it can "save your summer." The site also says that "if you love the mosquito repelling power of Off! but don't like the feel of a spray, then refillable Off! Clip-on is for you."

The bottom line

Off! Clip-on can undoubtedly fend off mosquitoes. The active ingredient "is apparently very effective," Moore says, and the fan is a clever way to spread the repellent where it's needed.

But if you're ever in a spot where mosquitoes block out the sky, and if Off! Clip-on is your only protection, the Healthy Skeptic has some advice: Run for cover.

I tested the device next to a brackish cattail pond in southeastern Montana, a place where mosquitoes dominate the food chain. In the name of research, I stood at the water's edge for a minute without any repellent. I had intended to systematically count the bugs that landed on me, but that plan fell apart in a fit of flailing, slapping and cursing.

Desperate for protection, I flipped the switch on my Clip-on. The fan started humming, and I eagerly waited for the result. Did it make any difference? Hard to say. Did Custer, at the Little Bighorn, miss the Sioux who were back tending camp? My clip-on probably kept a few bugs away, but plenty more were still content to feast on my legs, arms and neck. After a couple of minutes, I high-tailed it back to my car, ears still buzzing.

Perhaps I shouldn't have been surprised. Susan M. Paskewitz, a professor of entomology at the University of Wisconsin-Madison who specializes in mosquito control, had already warned me that dense swarms of mosquitoes tend to overwhelm devices that spread repellent in the air, including backyard foggers and candles. She says she always uses spray-on repellent when visiting the Boundary Waters region in Minnesota, another place where mosquitoes are in charge.

Off! Clip-on is unlikely to offer much relief to hikers or golfers or any other active people in mosquito country, Paskewitz says. As the product website warns, "if you move, allow a few minutes for the unit to rebuild its protection." In other words, it works best if you stay in one spot. "This sort of thing might be helpful if you're reading a book on a patio," Paskewitz says. "I wouldn't even bother trying it for backpacking."

Moore, too, says he'll stick with spray-on protection. Repellents containing DEET or picaridin are proven to be safe and effective, he says. (Metofluthrin is not available in sprays.) According to Moore, metofluthrin is probably a little more toxic to humans than DEET, although the Off! Clip-on should be safe as long as users don't inhale directly from the device.

Moore sees another potential problem. He, for one, wouldn't want to stake his mountain vacation on a cheap clip-on fan. He hasn't personally tested the device, but he suspects it wouldn't be hard to break. "Any time there's a mass-produced product made out of plastic, there are going to be a lot of failures," he says.

All of the moving parts in my device seemed to be doing their job. The clip didn't attach very tightly, however, and I had trouble keeping my shirt from blocking the fan. All in all, if I ever return to that pond on a summer evening, I'm definitely bringing bug spray. And maybe some full body armor.

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